The influence of synthetic pyrethroids on phytophagous mites and their natural enemies in apple orchards

[摘要] ENGLISH ABSTRACT:The effects of synthetic pyrethroids on the spider mite, Tetranychus urticae Koch,and its natural enemies was investigated. The pyrethroid cyfluthrin, sprayed forthe control of fruit weevil Phlyctinus callosus, did not cause mite outbreaks andwas not harmful to the predators when sprayed before they appeared on theapple trees. This spray also gave good control of thrips, bollworm (Heliothisarmigera) and fruit weevil (P. callosus). A late season spray of deltamethrinagainst codling moth, caused an increase in the phytophagous mite population.This was assosiated with a temporary reduction in the population level of thepredatory beetle, Oligota fageli.The plants found on the orchard floor were examined. The plant diversity waslow and plants that acted as hosts of phytophagous mites during the winter werescarce. However, Solanum nigum carried high mite populations and infected theadjacent apple trees. The plants were too few to have an effect on the wholeorchard.Eight synthetic pyrethroids were tested for repellency in a leafdisk dip and spraybioassay using T. urticae. Deltamethrin and fenvalerate caused no walk-off.Cyfluthrin and fluvalinate caused moderate walk-off and bifenthrin, cyhalothrinand lambda-cyhalothrin caused high walk-off.

[发布机构] Stellenbosch University